Amplitude Statistics Research Articles

Investigation of the RTN amplitude statistics of nanoscale MOS devices by the statistical impedance field method

This paper presents a numerical investigation of the random telegraph noise amplitude in nanoscale MOS devices based on the statistical impedance field method. This method allows a strong reduction of the computational burdens required for the calculation of the amplitude statistics with respect to conventional Monte Carlo models based on the numerical implementation of microscopic differences on the simulated device structure, allowing the exploration of lower probability levels. Despite a rather good estimation of the amplitude statistics, however, the method results in relevant inaccuracies when looking at the single Monte Carlo samples, due to the linear approximations involved.

3-D High-Frequency Ultrasound Backscatter Analysis of Human Articular Cartilage

High-frequency ultrasound is a promising method for non-invasive characterization of cartilage degeneration. Surface reflection and integrated spectral parameters are often used. In the work described here, human cartilage samples with varying degrees of degeneration were measured using a 40-MHz transducer. Backscatter signals originating from the superficial and transitional zones of cartilage were analyzed using amplitude, spectral and envelope statistical parameters and related to degenerative changes of the matrix given by the Mankin score. The results indicate an increased sensitivity of spectral slope and envelope statistical parameters to early matrix degeneration compared with conventional amplitude parameters. Furthermore, moderate correlations of chondrocyte number with backscatter amplitude and envelope statistics were observed, suggesting that at high frequencies, cells are one important scattering source in cartilage. An application of spectral and envelope statistical parameters to intra-articular ultrasound arthroscopy is conceivable and could improve the diagnostic potential of these examinations. Future studies are necessary to clarify the contributions of chondrocytes, extracellular matrix and collagen content to ultrasound backscatter to further improve the diagnostic potential of ultrasound for cartilage assessment.

A Markov-Middleton Model for Bursty Impulsive Noise: Modeling and Receiver Design

Transmission over channels impaired by impulsive noise, such as in power substations, calls for peculiar mitigation techniques at the receiver side in order to cope with signal deterioration. For these techniques to be effective, a reliable noise model is usually required. One of the widely accepted models is the Middleton Class A, which presents the twofold advantage to be canonical (i.e., invariant of the particular physical source mechanisms) and to exhibit a simple probability density function (PDF) that only depends on three physical parameters, making this model very attractive. However, such a model fails in replicating bursty impulsive noise, where each impulse spans over several consecutive noise samples, as usually observed (e.g., in power substations). Indeed, the Middleton Class A model only deals with amplitude or envelope statistics. On the other hand, for models based on Markov chains, although they reproduce the bursty nature of impulses, the determination of the suitable number of states and the noise distribution associated with each state can be challenging. In this paper, 1) we introduce a new impulsive noise model which is, in fact, a Hidden Markov Model, whose realizations exactly follow a Middleton Class A distribution and 2) we evaluate optimum and suboptimum detections for a coded transmission impaired by the proposed noise model.

Evaluation of Dose Uncertainty Associated With Real-Time Tracking IMRT Using Robotic Radiosurgery System

0.86 0.70 mm (AP). One patient exhibited relatively large motion amplitudes of 3.06 1.75 mm (SI), 0.41 0.36 mm (RL) and 2.46 1.44 mm (AP); 16% of the 2049 total retrieved amplitudes for this patient were over 5 mm. The amplitudes of the five fractions averaged from all patients were 0.92 0.72 mm, 0.99 0.62 mm, 1.14 0.91 mm, 0.98 0.82 mm, 1.18 1.10 mm in SI direction. Conclusions: In this study, respiratory motion in breast cancer patients treated with a hypofractionated approach was generally less than 5 mm. The interfraction motion pattern is relatively reproducible based on SI amplitude statistics. While we used real time motion tracking to treat patients, this study provides information about appropriate expansions for target motion using systems without real time correction. Author Disclosure: B. Zhao: None. X. Gu: None. C. Ding: None. Y. Yan: None. R. Timmerman: None. T. Solberg: None.

Amplitude statistics of ground clutter from town and hill observed by an S‐band radar

SummaryWe have observed ground clutter from a town and hills using an S‐band radar with a frequency of 3.05 GHz, a beamwidth of 1.8°, and a pulse width of 1.0 µs, located on the campus of the National Defense Academy in Yokosuka City. To investigate such ground clutter amplitude statistics, we introduce a compound distribution and the Akaike Information Criterion (AIC). We have found that the ground clutter amplitude obeys the compound lognormal distribution with shape parameters of σ1 = 0.424, σ2 = 0.232 for the entire data and the compound lognormal and compound log‐Weibull distributions with shape parameters of σ1 = 0.217 to 0.429, σ2 = 0.028 to 0.410, and c1 = 9.36 to 11.20 and c2 = 17.00 to 23.81, respectively, for data within the beamwidth of an antenna. The numbers for the minimum AIC (MAIC) of the compound lognormal and log‐Weibull distributions are 8 and 4, respectively. © 2013 Wiley Periodicals, Inc. Electron Comm Jpn, 96(7): 42–51, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.11407

The effects of internal tides on phase and amplitude statistics in the Philippine Sea

Moored oceanographic sensors and satellite altimetry has revealed energetic diurnal and semi-diurnal internal tides in the Western Philippine Sea. Because the internal tides have a complex spatio-temporal pattern and large vertical displacements, these waves have the potential for causing strong acoustic variability. This talk will present a tidal analysis of signal fluctuations from the PhilSea09 experiment in which broadband signals with a center frequency of 275 Hz and a bandwidth of 50 Hz were transmitted at the sound channel axis to a large aperture vertical array 180-km distant. Signal phase and amplitude statistics along distinct branches of the observed wavefronts will be analyzed and compared to ray-based model predictions using internal tide information obtained from moored oceanographic instruments at the source and receiver. Key issues are the acoustic effects of the internal tide nonlinearity, temporal stability, high mode structure, and complex horizontal interference patterns.

OBSERVATIONS OF CRAB GIANT PULSES IN 20-84 MHz USING LWA1

We report the detection and observed characteristics of giant pulses from the Crab Nebula pulsar (B0531+21) in four frequency bands covering 20-84 MHz using the recently-completed Long Wavelength Array Station 1 (LWA1) radio telescope. In 10 hours of observations distributed over a 72-day period in Fall of 2012, 33 giant pulses having peak flux densities between 400 Jy and 2000 Jy were detected. Twenty-two of these pulses were detected simultaneously in channels of 16 MHz bandwidth centered at 44 MHz, 60 MHz, and 76 MHz, including one pulse which was also detected in a channel centered at 28 MHz. We quantify statistics of pulse amplitude and pulse shape characteristics, including pulse broadening. Amplitude statistics are consistent with expectations based on extrapolations from previous work at higher and lower frequencies. Pulse broadening is found to be relatively high, but not significantly greater than expected. We present procedures that have been found to be effective for observing giant pulses in this frequency range.

Reliability estimation of ship's hull girder in probabilistic terms when ultimate strength is used as a failure mode

Using the ultimate strength as a failure mode, the hull girder reliability is calculated as the probability of the total bending moment (BM) acting on the ship's hull being greater than the ultimate hull girder moment. Both individual amplitude statistics and extreme value statistics are employed to derive the probability density function of the total hull girder BM as a sum of the still water and wave-induced bending moments probability density functions applying the convolution integral. The annual and lifetime probability density functions of the hull girder elastic and plastic section modulus are also derived and used as a base for determining the probability density functions of the first-yield and pure plastic BM. It is shown that the use of the first yield BM as a representative of the hull girder ultimate strength is reasonable only in the case when it is greater than ≈ 85% of the pure plastic BM. An example is given for a 25K DWT bulk carrier.

Sparse spectrum model for a turbulent phase

Monte Carlo (MC) simulation of phase front perturbations by atmospheric turbulence finds numerous applications for design and modeling of the adaptive optics systems, laser beam propagation simulations, and evaluating the performance of the various optical systems operating in the open air environment. Accurate generation of two-dimensional random fields of turbulent phase is complicated by the enormous diversity of scales that can reach five orders of magnitude in each coordinate. In addition there is a need for generation of the long "ribbons" of turbulent phase that are used to represent the time evolution of the wave front. This makes it unfeasible to use the standard discrete Fourier transform-based technique as a basis for the MC simulation algorithm. We propose a new model for turbulent phase: the sparse spectrum (SS) random field. The principal assumption of the SS model is that each realization of the random field has a discrete random spectral support. Statistics of the random amplitudes and wave vectors of the SS model are arranged to provide the required spectral and correlation properties of the random field. The SS-based MC model offers substantial reduction of computer costs for simulation of the wide-band random fields and processes, and is capable of generating long aperiodic phase "ribbons." We report the results of model trials that determine the number of sparse components, and the range of wavenumbers that is necessary to accurately reproduce the random field with a power-law spectrum.

Statistics of waves with different steepness simulated in a wave basin

Modulational instabilities induced by third-order nonlinear interactions among freely propagating waves can cause the statistics of various surface features to deviate significantly from the predictions based on the linear Gaussian and second-order models. This study analyzes deep-water waves with different initial steepness measured in a wave basin and characterized with such instabilities, and compares the statistics of wave heights, crest and trough amplitudes observed with a variety of theoretical approximations based on Gram–Charlier expansions. The results indicate that the theoretical approximations describe the empirical distributions observed reasonably well, for the most part. Further comparisons also show that the zero-up- and zero-down crossing heights of the largest waves observed in the experimental series do not exceed Miche–Stokes type upper limits.

MODELING SAR IMAGES BASED ON A GENERALIZED GAMMA DISTRIBUTION FOR TEXTURE COMPONENT

In the applications of synthetic aperture radar (SAR) data, a crucial problem is to develop precise models for the statistics of the pixel amplitudes or intensities. In this paper, a new statistical model, called simply here Gii, is proposed based on the product model by assuming the radar cross section (RCS) components (texture components) of the return obey a recently empirical generalized Gamma distribution. Meanwhile, we demonstrate theoretically that the proposed Gii model has the well-known K and G - distributions as special cases. We also derived analytically the estimators of the presented Gii model by applying the \method-of-log-cumulants (MoLC). Finally, the performance of the proposed model is tested by using some measured SAR images.

Suppression of Log-Normal Distributed Weather Clutter Observed by an S-Band Radar

We have observed weather clutter containing targets (ships) using an S-band radar with a frequency 3.05 GHz, a beam width 1.8°, and a pulsewidth 0.5 μs. To investigate the weather clutter amplitude statistics, we introduce the Akaike Information Criterion (AIC). We have found that the weather clutter amplitudes obey the log-normal, Weibull, and log-Weibull distributions with the shape parameters of 0.308 to 0.470, 4.42 to 4.51, and 15.91 to 16.44, respectively, for small data within the beam width of an antenna. We have proposed the log-normal/CFAR circuit modified a Cell-Averaging (CA) LOG/CFAR circuit. It is found that weather clutter is suppressed with improvement of 51.58 dB by log-normal/CFAR. As a result, we have showed that weather clutter observed by S-band radar does not obey the Rayleigh distribution and our log-normal/CFAR circuit has an effect on suppression of clutter and detection of target, while conventional LOG/CFAR circuit does not. In addition, if our circuit can be realized, we will have an advantage economically.

Deterministic forward scatter from surface gravity waves

Deterministic structures in sound reflected by gravity waves, such as focused arrivals and Doppler shifts, have implications for underwater acoustics and sonar, and the performance of underwater acoustic communications systems. A stationary phase analysis of the Helmholtz-Kirchhoff scattering integral yields the trajectory of focused arrivals and their relationship to the curvature of the surface wave field. Deterministic effects along paths up to 70 water depths long are observed in shallow water measurements of surface-scattered sound at the Martha's Vineyard Coastal Observatory. The arrival time and amplitude of surface-scattered pulses are reconciled with model calculations using measurements of surface waves made with an upward-looking sonar mounted mid-way along the propagation path. The root mean square difference between the modeled and observed pulse arrival amplitude and delay, respectively, normalized by the maximum range of amplitudes and delays, is found to be 0.2 or less for the observation periods analyzed. Cross-correlation coefficients for modeled and observed pulse arrival delays varied from 0.83 to 0.16 depending on surface conditions. Cross-correlation coefficients for normalized pulse energy for the same conditions were small and varied from 0.16 to 0.06. In contrast, the modeled and observed pulse arrival delay and amplitude statistics were in good agreement.

Modeling and Simulation of Coherent Sea Clutter

This paper describes a new technique for modeling and simulating the coherent returns from radar sea clutter, based on the compound K-distribution model for clutter amplitude statistics. Using observations of recorded Doppler spectra, a simple method is proposed for characterizing the temporal variations of the Doppler spectrum observed in a single-range cell. It is shown that simulations based on this model can reproduce the main statistical features observed in real measurements.

Unsupervised Amplitude and Texture Classification of SAR Images With Multinomial Latent Model

In this paper, we combine amplitude and texture statistics of the synthetic aperture radar images for the purpose of model-based classification. In a finite mixture model, we bring together the Nakagami densities to model the class amplitudes and a 2-D auto-regressive texture model with t-distributed regression error to model the textures of the classes. A non-stationary multinomial logistic latent class label model is used as a mixture density to obtain spatially smooth class segments. The classification expectation-maximization algorithm is performed to estimate the class parameters and to classify the pixels. We resort to integrated classification likelihood criterion to determine the number of classes in the model. We present our results on the classification of the land covers obtained in both supervised and unsupervised cases processing TerraSAR-X, as well as COSMO-SkyMed data.

A Real-Time and Offline Quality Control Methodology for SeaSonde High-Frequency Radar Currents

Abstract A near-real-time and offline quality control methodology for SeaSonde systems is proposed. It is applied on radial current maps and is based on the determination of the signal-to-noise ratio (SNR) values of the Doppler lines that contribute to the hourly radial current at each range-bearing (R, θ) pair, under the assumption that SNR is a proxy for radar data quality. The retrieval of the sequence of Doppler lines is performed through a minimization procedure that takes advantage of the statistical descriptors output in the short-term radial maps. The separation of the contributing Doppler velocities into valid observations and anomalous velocities is based on their spectral quality factor and on a range-dependent noise threshold derived from statistics (average and standard deviation) of the signal amplitudes in the tails of the Doppler spectra. The final product of the quality control procedure is a radial current map, in which Doppler velocities are weighted by their SNR values and their spectral quality factors, and averaged to produce an output that is fully compatible with the proprietary software. This procedure is fast, despite the fact that a large number of combinations might be required during the retrieval of the Doppler lines, and effective, because it removes both evident spikes as well as Doppler velocities that are not clearly identified as anomalous velocities. In principle, this approach can be used to fill gaps in the radar coverage without the need for interpolation in time or space, proved that the Doppler velocities satisfy predetermined SNR constraints.

Logarithmic intensity and speckle-based motion contrast methods for human retinal vasculature visualization using swept source optical coherence tomography

We formulate a theory to show that the statistics of OCT signal amplitude and intensity are highly dependent on the sample reflectivity strength, motion, and noise power. Our theoretical and experimental results depict the lack of speckle amplitude and intensity contrasts to differentiate regions of motion from static areas. Two logarithmic intensity-based contrasts, logarithmic intensity variance (LOGIV) and differential logarithmic intensity variance (DLOGIV), are proposed for serving as surrogate markers for motion with enhanced sensitivity. Our findings demonstrate a good agreement between the theoretical and experimental results for logarithmic intensity-based contrasts. Logarithmic intensity-based motion and speckle-based contrast methods are validated and compared for in vivo human retinal vasculature visualization using high-speed swept-source optical coherence tomography (SS-OCT) at 1060 nm. The vasculature was identified as regions of motion by creating LOGIV and DLOGIV tomograms: multiple B-scans were collected of individual slices through the retina and the variance of logarithmic intensities and differences of logarithmic intensities were calculated. Both methods captured the small vessels and the meshwork of capillaries associated with the inner retina in en face images over 4 mm2 in a normal subject.

Statistics of low-frequency normal-mode amplitudes in an ocean with random sound-speed perturbations: Shallow-water environments

Second- and fourth-moment mode-amplitude statistics for low-frequency ocean sound propagation through random sound-speed perturbations in a shallow-water environment are investigated using Monte Carlo simulations and a transport theory for the cross-mode coherence matrix. The acoustic observables of mean and mean square intensity are presented and the importance of adiabatic effects and cross-mode coherence decay are emphasized. Using frequencies of 200 and 400 Hz, transport theory is compared with Monte Carlo simulations in a canonical shallow-water environment representative of the summer Mid-Atlantic Bight. Except for ranges less than a horizontal coherence length of the sound structure, the intensity moments from the two calculations are in good agreement. Corrections for the short range behavior are presented. For these frequencies the computed mode coupling rates are extremely small, and the propagation is strongly adiabatic with a rapid decay of cross-mode coherence. Coupling effects are predicted to be important at kilohertz frequencies. Decay of cross-mode coherence has important implications for acoustic interactions with nonlinear internal waves: For the case in which the acoustic path is not at glancing incidence with a nonlinear internal-wave front, adiabatic phase randomizing effects lead to a significantly reduced influence of the nonlinear waves on both mean and mean square intensity.

Sea Clutter Amplitude Statistics Analysis by Goodness-of-Fit Test

This paper provides a quantitative method for analyzing the amplitudes statistics of sea clutter by goodness-of-fit (GOF) tests. It first introduces several well-known GOF tests, and then employs them to test the amplitude statistics of recorded live sea clutter. Results confirm that the amplitudes of recorded live sea clutter can be well modeled by the Weibull and K distributions.

Amplitude Statistics of Sea Clutter by MDL Principle

Amplitude Statistics of Sea Clutter by MDL Principle